Coil



May 1, 1928. I 1,668,302

F. AUTY COIL Original Filed March 5, 1924 Patented May 1, 1928 UNITED STATES FRANK AU'IY, OF NEW YORK, N. a.

COIL.

Original application filed March 5, ma, Serial September 11, 1924.

My present invention is primarily concerned with toroidal coils, a more specific application being to core-less toroidal wire coils.

In their application for wireless receiving purposes, the theoretical and practical advantages of core-less or air core toroidal coils have been freely recognized by those skilled in the art, but difficulty of economi cal production of such coils, satisfactory in mechanical construction and in operation, has prevented their general adoption.

It is accordingly among the objects of the invention to provide from wire of small gauge, a toroidal coil, satisfactory in its electrical characteristics, capable of sustaining itself in a firm and durable structure and capable of resisting rough handling though devoid of a core.

In the preferred embodiment, contiguous convolutions are arranged in side by side engagement at the outer periphery of the coil without lapping, said convolutions being, however, lapped with respect to each other to progressively greater extent from the outer to the inner periphery, to a maximum degree of lapping at the latter region, the number of layers at said inner periphery being substantially equal to the ratio of the outer to the inner diameter of the torus. By this construction, no deleterious twisting of the wire or fraying of the insulation is engendered-in the process of making up the coil, so that wire of the gauge ordinarily used for variocouplers, variometers or transformers is suitable and the coil will be maintained in a firm and durable structure capable of resisting rough handling though devoid of a core and further though devoid of an enclosure of adhesive tape.

Although I claim in the present application, the coil per se regardless by which method it is formed, it is preferably produced according to the method claimed in my copending application, Serial No. 697,063, filed March 5, 1924, of which the present application is a division.

Other objects and features of the invention'will be in part obvious and in part pointed out hereinafter.

In the accompanying drawings in which are shown one or more of various possible embodiments of the several features of the invention,

Fig. l is a transverse sectional view No. 697,063. Divided and this application filed Serial No. 737,099.

through a toroidal coil shown mounted on an appropriate supporting fixture.

Fig. 2 is a plan view of the toroidal coil,

Fig. 3 is an end view thereof,

Fig. 4 is a view in cross-section on a greatly enlarged scale illustrating the lapping of the convolutions,

Fig. 5 is a fragmentary view of one form of mandrel for making the coil,

Fig. 6 is a sectional view taken along the line (i(3 of Fig. 5,

7 is a diagrammatic view illustrating the method of making the mandrel,

Fig. 7 is a fragmentary view of the tool used in cutting the mandrel,

Fig. 8 is a view in transverse cross-section taken along the line 8-8 of Fig. 6.

Similar reference characters refer to similar parts in different views of the drawings.

Referring to the drawings, I have shown in Figs. 1, 2 and 3 in outline, the general form of core-less toroidal coil with which my invention is primarily concerned, said coil being illustratively indicated with an outer periphery 10 substantially double the inner periphery 11 thereof and held in assembled relation by a peripheral length of tape 12 connected about the outer periphery thereof, the terminals of the coil protruding as at 18. The coil as shown, would be mounted on a bracket including a pair of washers 14 and 15 near opposite sides thereof, substantially closing the inner periphery thereof and connected by a bolt 16 which tends to press said washers inward to securely grip the torus and which serves for mounting the coil in manner that will readily be understood.

The construction of the toroidal coil will be more easily comprehended from the method of producing the same which will be first set forth. The mandrel by which the torus is produced, includes a. winding surface modified from the cvlindrical form as will appear best from F 5 to 8. The mandrel construction will be mostreadily understood from the method by which it, in turn, is made. For this purpose, a tube of diameter equal to the inner diameter of the torus convolutions is mounted eccentrically, for instance, on centers 17 within a lathe (not shown). A tool 18 is employed having a cutting edge of buttress-thread type, that is a V-shaped cutting edge with one side 19 substantially longitudinally of the tool shank and the other side'QO oblique as best shown in Fig. 7 The tool being held by an appropriate rest (not. shown) so that its point substantially engages the mandrel at the element thereof nearest the eccentric mount, the mandrel is. rotated, whereby, as will be easily understood, a peripheral groove or notch l-shaped in cross-section will be cut, of maximum depth as at 21 at the side nearest the. eccentric mount, progressively decreasing to a minimum or zero depth at the side 22 diametrically opposite thereto.

The operation set 'forth is repeated at intervals corresponding to the cutting width of the cutting tool, so that the entire effective length of the mandrel will be notched, as best shown in 'Figs. 5 and 8. It will be seen that as the depth of cut decreases, peripherally about the mandrel from the maximum at one side thereof, the width thereof decreases correspondingly. A plane oblique edge 23 is therefore formed at each peripheral notch. The portion 24 to the rightof the edgef23 remains cylindrical. The portion 25 to the left of oblique edge 23 is il shaped in cross-section of maximum depth and width at the portion corresponding to the side 21 as shown in Fig. 5 and gradually decreasing both v in depth and width progressively about the mandrel in both directions to Zero at the diametrically opposite portion, corresponding to side 22.

The mandrel described being mounted concentrically in a lathe or equivalent driving means, the wire or other element 26 to be wound thereon is applied at the base of one of the notches. hen the 'mandrel' is now rotated the wire will form substantially a helix. Consecutive convolutions thereof will be in lateral contact with each other along straight element at one side of the mandrel while at the diametrically opposite element "the consecutive convolutions will climb up the incline of the notch until after the apex of the notch is reached, the nextconvolution will drop into the base of the succeeding notch for consecutive turns to build up along the corresponding notch incline. Thus, the conformations of the successive convolutions will vary to correspond with the V mandrel, the convolutions engagingthe bases moved from within the Wound coil after the adhesive tape 12 has been applied to the latter. Thereupon the generally helical coil of wire can'be easily curved to bring its op- )osite ends into en a ement with each other a: c:

an appropriate generally conical fixture (not shown) being preferably used asa guide or template for this purpose, whereupon the ends are attached together by a short connecting piece of adhesive tape with the wire terminals 13 projecting. If desired, length 120 of tape similar to tape 12 is provided at the insideof the outer periphery of the torus, said lattertape being, of course, applied on the mandrel before. the wire is wound.

It will be seen that the coil when removed from the inandreland before it is curved into torus form, will present a segmented appearance, the convolutions being in contact with eachother at the element appearing at the lowerpart of Fig. 5 but arranged in groups other elements thereof. By reason of this segmental or stepped conformation, as the coil is curved to form the torus, the successive segmented groups will readily lap or telescope with respect to each other, the convolutions of smaller diameter entering into the neighboring convolutions of larger diameter, the extent of entry or telescoping being, of course, a maximum at the inner toroidal coil, than ifthe turns were cylindrical at the part of the helix that is. to be curved into the outer periphery of the toroidal coil. Moreover, tape 12 also will develop no folds or wrinkles in curving into a cylindrical loop as the torus is formed.

1n the specific toroidal coil illustratively shown, the inner periphery is one-third the outer periphery, so that only one-third, as many turns can be exposed thereat,' in lateral contact with each other than at the outer periphery. Accordingly'the succesive convolutions are all exposed in lateralcontact with each other to form the outer periphery of the torus, and only'every third convolution will be exposed at the inner periphery, the intervening turns being lapped tjliereat in the interior of the torus. This is clearly shown in Fig. 4:, where the consecutive turns o bear consecutive exponents, the diametrically opposlte sides of the same turns C be flattened Ill) iso

having the same exponents. Between the inner and outer peripheries of the torus, by reason of the intermediate width and depth of the notches of the forming mandrel, the degree of telescoping or lapping between the successive contacting groups of convolutions will vary in accordance with the diameter of the torus thereat, so that the unit is self-sustaining and will not open or be dis torted even under substantial pressure, the convolutions being in mutually trussing relationship.

It *ill, of course, be understood that the number of convolutions at each step or notch incline 27 should correspond approximately to the ratio of the outer to the inner periphery of the torus. By the use of a mandrel with corresponding width of notch relative to the diameter of the wire, a toroidal coil with any ratio of outer to inner diameter can be produced.

By my method. the convolutions are conformed to naturally or inherently enter into the telescoping relationship set forth, as the helix is curved to form the torus, so that no substantial strain is exerted on the wire and no friction or rubbing is engendered tending to fray the wire insulation. Accordingly, I avoid the use of heavily isulated wire, but the wire ordinarily used for inductance coils in amateur wireless receiving apparatus is suitable, and said relatively thin wire, by reason of the mutual trussing relationship of its turns forms a rugged durable self-sustaining torus coil, though taped only at its outer periphery, and even this is not necessary.

To render the mandrel collapsible, any appropriate construction may be provided. In a preferred embodiment, the stepped cutting mandrel tube is slit longitudinally in a number preferably four segments 30, said segments embracing a solid cylindrical core 31, which may be of vulcanite and which has protruding metal center pieces 32. The segments are maintained assembled upon the core by and caps 33 preferably formed with integral spacing iins 34 to maintain the uniformity of the narrow gap 35 between the successive mandrel segments. It follows, therefore, that after the coil has been wound on the mandrel, the latter is collapsed by simply removing one of the end caps and drawing out the core whereupon the multiplicity of segments of the mandrel tube will collapse within the coil and can be removed without in any way distorting the wound product.

In the present application, I claim my coil per se regardless by what method it may be produced, although it is preferably made by the method herein described and separately claimed in my copending parent application above identified.

It will also be understood that although the. consecutive turns of the helix preferably engage laterally the outer periphery of the toroidal coil, this is not necessarily the case. Gaps may be left between consecutive turns,

particularly, if the coil is mounted on and curved with a plastic core.

lVhile I have merely described in the foregoing a toroidal coil and the method of making the same, the principleof the invention could be readily applied to simple tuning coils, to variocouplers, or variometers including two semi-toroidal coils, and to transformers, especially to radio-transformers. In the latter application, the primary coil of lesser number of convolutions could be wound in ordimiry fashion about the secondary after the latter had been made on the mandrel. In some of the applications noted, it may be desirable to form the individual turns of the toroidal coil generally elliptical rather than generally circular. For this purpose, the mandrel would be formed as a generally elliptical cylinder, with the notches heretofore described. Although the preferred application is to coreless or air-core coils, the invention is not limited to this application, but may be applied. to coils with cores performing either a mechanical o a. magnetic function or both.

The invention is not limited in its application to wireless apparatus but can be applied to other uses and many of the aspects thereof are more broadly applicable to winding and reeling apart from electrical application.

It will thus be seen that there is herein described apparatus in which the several features of this invention are embodied, and which apparatus in its action attains the various objects of the invetnion and is well suited to meet the requirements of practical use.

As many changes could be made in the above construction and many apparently widely different embodiments of this inven tion could be. made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters-Patent of the United States is 1. A self-sustaining toroidal coil comprising a succession of convolutions in a cyclic arrangement, the successive convolutions lapped at the inner circumference of the torus to expose substantially only one convolution of each cycle at said inner periphery, the extent of lapping decreasing progressively from the inner periphery of the torus in accordance with the increasing diameter to substantially side by side engage ment of the convolut-ions without lapping at the outer periphery of the torus, and binding means extending eircumferentially of the torus substantially at right angles to the several convolutions and retaining the torus against separation of its turns, the successive convolutions of the torus being free from mechanical attachment to each other at all parts thereof other than at said binding means. i i

2. A self-sustaining toroidal coil including a wire arranged in convolutions in a single layer at the outer periphery of the torus, said convolutions lapped at the inner periphery of the torus in a number of layers,

substantially equal to the ratio ofthe outer to the inner diameter of the torus, and binding means extending about the outer periphery of the torus and of Width less than the diameter of the torus convolutions to retain said convolutions against separation, the convolu'tions being freely exposed at the inner-periphery of the torus.

3. itself-sustaining toroidal coil including a continuous length of Wire arranged in convolutions in a single layer at the outer periphery of the torus, said convolutions lapped at the inner periphery ofthe torus in a number of layers substantially equal to the'ratio of the outer to the inner diameter of the torus and binding means retaining said torus against separation of the convolutions thereof, said binding means extending adjacent the outer periphery of the. torus and freely. exposing the. major part of said torus. V

4. -A toroidal coil comprising a single conlessees tinuous length of coiled Wire having successive convolutions thereof substantially in contact witheach other at the outer periphery of the torus and lapped with respect to each other in groups to progressively greater extent "from the 'outer per'iphery of the torus to a maximum degree of lapping atthe inner periphery of the'torus,and adhesive binding means extending about the outer periphery of the torus and attaching the successive convolutions thereat against separation, thereby retaining the uncovered inner ,portions of the convolutions making up the torus'in fixed assembled self-sustaining relation. I

5. A toroidal coil comprising a single continuous length of coiled Wire having successive convolutions thereof substantially'in Contact with each other at the outer periphery of the torus andlapped with respect to each other in groups to progressively greater extent from the outer periphery of the torus toa maximumdegree of lapping at the inner periphery of the torus, the turns of the toroidal coil 'being flattened at the outer peripheries thereof, and a length of adhesive tape extending about the coil at the flattened portions of the convolutions,

.thereby retaining "the uncovered inner portions of the convolutions making up the torus in fixed assembled self-sustaining relation.

Signed at'NeW York city, in the county of New York and State of'NeW York this 28th day of June A. .Df1-924i.

FRANK AUTY. 

